Mat. Res. Bull., Vol. 25, pp. 691-698, 1990. Printed in the USA. 0025-5408/90 $3.00 + .00 Copyright (c) 1990 Pergamon Press plc. CRYSTAL GROWTH AND INVESTIGATION OF THE SOLID SOLUTIONS OF THE SYSTEM CuGe2P3-I2-IV-VI3* M. S. Omar Department of Physics College of Science, University of Salahaddin Arbil, IRAQ (Received April 28, 1989; Communicated by H. Tu) ABSTRACT The compounds Cu2GeS 3, Cu2SiS 3 and Cu2SiSe 3 were dissolved in the ter- nary compound CuGe2P 3. A modified Bridgman technique was used in the preparation, and good quality single crystals were grown for single phase samples. A complete solid solution for the system CuGe2P3-Cu2GeS 3 was found, with lattice parameters changing from 5.3678~ to 5.2895~ for 90% CuGe2P 3 and obeying Vegards law. In the CuGe2P3-Cu2GeSe 3 system the existence of the solid solution appears in the region of 0.25~x~0.9 when x is CuGe2P 3. However, the compound CuGe2P 3 does not form any solid solution with the compounds Cu2SiS 3 and Cu2SiSe 3. MATERIALS INDEX: alloys, copper, germanium, phosphorus Introduction Ternary I2-IV-VI 3 compounds were first reported by Goodman (I), who syn- thesized Cu2SnSe3, Cu2SiSe 3 and Cu2SnTe 3. Averkiva and Vaipolin (2) studied a series of I2-IV-Vi 3 compounds with I=Cu, IV=Sn and VI=S, Se or Te, and reported a sphalerite structure for all of them. The same structure was reported for compounds containing Cu, Ge and Sn in another investigation (3), and a large group of ternary chalcogenides was studied by Rivet (4) and others (5). They synthesized the compounds by fusion of the component elements with a i% excess S, Se or Te of the stoichiometric. The existence of a chalcopyrite solid solution has been established (6) in compositions ranging from pure Cu2GeSe 3 to 2Cu2GeSe 3 in the system Cu2GeSe 3- Cu2SnSe 3. Others (2) have shown that the system Cu2GeSe3-Cu2GeTe 3 forms non- equilibrium, substitutional solids throughout the entire range of compositions. Cu2GeSe 3 can also form solid solutions with GaAs. Goryunova (7) reported on single crystals of an alloy consisting of 20% Cu2GeSe 3 and 80% GaAs in a sphal- erite structure, using the method of gas transport reaction. It has been re- ported that this is a solid solution for the system Cu2GeSe3-Ga2Se 3 of the range 0.4<x<i, where x is the mole fraction of Cu2GeSe 3 (8). *This paper is dedicated to the memory of Dr. B.R. Pamplin of the University of Bath, who died in the early days of 1987. 691